Asked by reporters if he had proposed anybody's name for the post of Vice-President, Karunanidhi said it is "not my job".
"I think it is not my job. I considered it my duty to propose the name of our front's (UPA) candidate for the President's post. I have done that," Karunanidhi said.
The DMK chief had hosted a dinner in honour of Mukherjee on Saturday when the latter launched his Presidential campaign from Chennai.
Karunanidhi had hinted at supporting the former finance minister for the country's top post even before UPA officially announced his candidature.